The U.S. can be powered 100% by renewable energy. How do we get there?

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A study by Stanford scholar Mark Z. Jacobson and a team of researchers at both Stanford University and the University of California at Berkley in 2015 created a road map for a 100% renewable future. Ambitious? Sure. Unlikely? Perhaps.

Skeptics shot it down, optimists pointed to it for inspiration. Since 2015, it’s been basically debunked. (It made deep assumptions about the hydroelectric availability that’s even technically achievable in the U.S.) But this study brought a 100% renewable future to the forefront, and it made a point to say that it wasn’t just possible, it was affordable.

According to the study’s analysis, 80% to 85% of our energy demand can be supplied from wind, water, and solar by as early as 2030. The remaining 15% to 20% would take another 20 years — as long as everything goes right — which is probably the best-case scenario as it stands now. This included a rapid uptake of electrifying everything — vehicles, aircrafts, rail and bus transport, and all appliances — not to mention one of the most coordinated efforts of government action probably ever.

To say it’s ambitious is probably an understatement.

But, despite all of these assumptions, one thing remained. The first 80% appears to be the easy part, and it’s one thing most engineers, scientists, and researchers agree on — skeptics and optimists alike. So, let’s see what it takes to get there first.

A unified grid

To begin producing more renewable energy, the renewable energy we generate must have somewhere to go. Today, that’s not exactly the case.

Right now, our existing grid is divided into three major parts and exchanges very little power between them: the western interconnection, the eastern interconnection and Texas. A national grid would allow the states that produce more renewable energy than they can consume to export it to states that don’t.

Let’s take wind energy for example. According to a report from the Wind Energy Association, 15 states account for 87% of the wind energy potential but are projected to only account for 30% of the nation’s energy demand by 2050. Our transmission infrastructure and our grid are in the way.

It comes as no surprise that the 15 states that generate the most wind energy lie in the central-U.S.: Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, Minnesota, Iowa, Missouri, Arkansas and Louisiana.

It should also come as no surprise that the demand for this energy lies outside the renewable-rich region.

By connecting these regions together via high-voltage transmission lines, congestion can be relieved on both ends of the line. The central states can produce as much renewable energy as possible without worrying if it’s going to be consumed or not, maximizing the use of generated renewable energy while balancing load demands across the country.

What will it take to unify the grid and unlock the full renewable potential of this region and the U.S.?

Wood Mackenzie says we need to double the network of our existing transmission lines from 200,000 miles to 400,000 miles. Not only would this help unify the grid, but it’d also establish a transmission infrastructure that could actually transfer the amount of energy required to power the U.S. completely on renewable energy alone.

The sooner this happens, the better. Right now, 20 states have already committed to 100% renewable energy goals, and virtually all of them lie outside of the wind-energy-rich central U.S.: Arizona, Connecticut, Florida, Georgia, Illinois, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, North Carolina, Oregon, Pennsylvania, Wisconsin, Virginia, Washington, California, New Mexico, New York, Maine.

Overbuild electrical generation capacity

Okay, so if reaching 80% of total energy generation through renewable sources is feasible within the next 10 years, what about the last 20%?

Forecasting load demand and generating 100% of our power through renewable energy is certainly a challenge. The best way to overcome it? Overbuild… by a lot.

In Jacobson’s 2015 study, the authors estimate that the average U.S. energy demand will reach 2.6 TW by 2050. How much energy capacity do we need to account for that much energy demand? About 2.5 times as much, or 6.5 TW of total energy capacity. Today, we’re at about 1.2 TW.

To give an idea of how much that actually is, Jacobson and his team laid out one of the more affordable ways that can be done, focusing solely on wind, water, and solar:

• 328,000 new onshore 5 MW wind turbines (providing 30.9% of U.S. energy for all purposes)
• 156,200 off-shore 5 MW wind turbines (19.1%)
• 46,480 50 MW new utility-scale solar-PV power plants (30.7%)
• 2,273 100 MW utility-scale CSP power plants (7.3%)
• 75.2 million 5 kW residential rooftop PV systems (3.98%)
• 2.75 million 100 kW commercial/government rooftop systems (3.2%)
• 208 100 MW geothermal plants (1.23%)
• 36,050 0.75 MW wave devices (0.37%)
• 8,800 1 MW tidal turbines (0.14%)
• 3 new hydroelectric power plants (all in Alaska)

Of course, there are many generator mixes to help us reach 100% renewable energy when overbuilding energy capacity by 2.5 times as much as what’s needed. The point remains, if we want to hit 100% renewable energy while excluding alternative methods of getting there, such as nuclear, natural gas, etc., then this is one way of building a sustainable energy system.

Waste: the heart of the problem

Renewable energy is highly variable, referred to as variable renewable energy (VRE).

The sun shines, the wind blows — until it doesn’t. On the flip side, sometimes it’s too sunny out, or too windy. This leads to large spikes in power that dip way below and rise way above consumer energy demand. However, because renewable energy is variable, it can’t be dispatched, meaning it can’t be turned on and off. If the energy can’t be absorbed into the supply or transmitted along the line, it’s wasted.

One of the best ways to make sure VRE is not wasted? Store it.

In a paper written by Benjamin Kroposki, the Director of the Power Systems Engineering Center at the National Renewable Energy Laboratory (NREL), he examines how to integrate high levels of VRE into electric power systems despite the variability and uncertainty. He comes to a rather simple conclusion, but an important one.

“Energy storage” Kroposki writes, “can help deal with all aspects of the integration challenge, but also is one of the most expensive options. At the very highest levels of VRE penetration, energy storage is crucially important to allow for significant energy shifting and grid availability when the renewable resource is not available.”

If the energy can’t be dispatched and it can’t be distributed along the line, storing it is one of the best ways to handle consecutive days of low wind or solar availability.

The good news? According to the Environmental Defense Fund, the energy storage market is expected to grow by 9 times its size by 2022.

This growth has already helped accelerate the shift to cleaner energy. Since 2014, there’s been a staggering 60%+ price drop in utility-scale energy storage. Today, thanks to more cost-effective storage options, utilities are now moving toward renewable energy (and energy storage) in favor of new natural gas power plants.

The Renewable Energies Division at City Electric Supply sees this cost reduction as a huge catalyst for the industry.

“We have seen tremendous growth in the battery storage sector over the past couple of years in both our utility division and our residential and commercial division,” Robbie McNamara said, who is the National Renewable Business Development Manager at City Electric Supply.

“Since the initial drastic cost reduction — and continued reduction — in lithium-ion technology, as well as the collected data proving a palatable ROI when coupling storage with renewable power, adding energy storage to new projects and retrofitting it onto existing solar farms is now the new norm.”

Is renewable reliable?

Because renewable energy is highly variable, is it reliable? Short answer, very.

It’s true that there may be days where we don’t see much wind or don’t capture as much power from the sun, but there is nonvariable energy generation happening in the background to support limited solar or wind availability.

Hydroelectric and geothermal energy can be ramped up and down to meet demand while providing a more stable backbone to VRE.

What happens in the event of a storm or other natural disaster?

For one, coal, natural gas, and oil operations can be severely disrupted during an emergency event and require a lot of manpower to bring back online, especially if there is a natural gas or oil spill that not only disrupts our power supply but also pollutes the environment around it.

With renewable energy, it’s much safer and easier to bring wind turbines and solar panels back online than it is to fix pipelines. In terms of disaster relief, a single national grid will provide even more stability to disaster-prone areas, and if each region is connected, areas that cannot generate their own power can draw from the overall supply.

How much will this cost?

The question on everyone’s mind. Given that the energy industry is motivated enough to decarbonize the grid and agrees to shut off natural gas plants, say, within the next 10 to 20 years, how much will it cost to go renewable?

Analysts at Wood Mackenzie crunched the numbers and found that it’ll cost around \$4.5 trillion, assuming current technology. The real kicker? The price tag doesn’t change if the U.S. completes the transition in 10 years or 20.

And what if we keep nuclear energy in the mix? It’d still cost in the ballpark of \$4 trillion.

The steps to getting to a 100% renewable future, however, remains the same with recent findings and what’s been mentioned above.

First, we need to dramatically build out wind and solar capacity.

Second, we need to add plenty of storage for energy availability.

Third, we need to overhaul the grid by doubling the miles of high-voltage transmission lines from 200,000 miles to 400,000 miles.

The next question remains. If it’s going to cost the same in 10 years as it will in 20, what’s the point in waiting?

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Starting in 2018, Brad McElroy has worked as a copywriter for City Electric Supply. He writes regularly about the electrical industry, covering a range of topics that include anything from smart tech and lighting to industrial developments and renewable energy.

The views and opinions expressed in this article are the author’s own, and do not necessarily reflect those held by pv magazine.

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